Substance use disorders (SUDs) are highly comorbid with posttraumatic stress disorder (PTSD; Kessler et al., 1995), and this comorbidity is associated with significant problems, including a greater likelihood of substance use treatment failure (e.g., Ouimette, Brown et al., 1998). Further, research suggests that it is not traumatic exposure per se that puts substance users at greater risk for worse outcomes, but instead the development of PTSD (Chilcoat & Breslau, 1998). Despite evidence that there is something unique to PTSD that negatively affects the course and outcome of substance use treatment, studies have yet to identify the specific mechanisms that may influence the maintenance of substance use among individuals with PTSD. It has been suggested that selective attentional biases may play a central role in the development and maintenance of drug use behavior, as well as relapse to substance use following treatment (Marlatt & Gordon, 1985; Robinson & Berridge, 1993; Tiffany, 1990). This may especially be the case among substance users with PTSD, as research suggests that substance users with PTSD may be more susceptible to become sensitized to drug cues as a result of the negative reinforcement substance use provides in regard to PTSD symptom reduction. That is, consistent with Robinson & Berridge's (1993) incentive-sensitization model, as drugs are increasingly used to self-medicate PTSD symptoms, drug-related stimuli may become more salient and "attention-grabbing" due to their ability to predict reward (i.e., symptom reduction). This is especially likely when PTSD symptoms are being experienced, given the potential for substances to provide immediate relief from certain PTSD symptoms, such as hyperarousal or re-experiencing. Nevertheless, this has not been tested directly. To address this gap in the literature, we will examine if crack/cocaine users with PTSD in an inner-city residential treatment center exhibit a greater attentional bias for drug-related cues, compared to their counterparts with a history of trauma but no current or lifetime history of PTSD, following exposure to a trauma cue. Evidence for greater selective attention for crack/cocaine imagery in the presence of trauma-related cues among PTSD- SUD participants would suggest a possible pathway through which PTSD is associated with greater relapse rates, and has the potential to aid in the eventual development of effective interventions that could be integrated into standard treatments utilized in residential treatment centers. Further, by utilizing an inner-city minority population, this study has the potential to reduce disparity associated with research in and the treatment of PTSD and SUDs among inner-city substance users. This study has specific relevance for underserved and understudied populations. The identification of heightened drug-related attentional biases following exposure to a trauma cue among crack/cocaine users with PTSD has the potential to aid in the development of effective interventions that could be integrated into standard treatments utilized in inner-city residential treatments settings, thus reducing vulnerabililty for treatment failure within this population. Consequently, this study will have tremendous public health benefits. [unreadable] [unreadable] [unreadable]